In ion implantation systems, an ion beam is directed towards a work piece (e.g., a semiconductor wafer, or a display panel) to implant ions into a lattice thereof. Once embedded into the lattice of the workpiece, the implanted ions change the physical and/or chemical properties of the implanted workpiece region. Because of this, ion implantation can be used in semiconductor device fabrication, in metal finishing, and for various applications in materials science research.
An ion beam often has a cross-sectional area that is significantly smaller than the surface area of a workpiece to be implanted. Because of this, typical ion beams are scanned over the surface of the workpiece until a desired doping profile is achieved in the workpiece. For example, FIG. 1A shows a cross-sectional view of a conventional ion implantation system 100 where an ion beam 102 traces over a scan path 104 to implant ions into the lattice of a workpiece 106. While scanning the ion beam over the scan path 104, the ion implanter makes use of a first axis 108 and a second axis 110 that collectively facilitate two-dimensional scanning over the workpiece surface. In this system 100 there are sufficient scans per unit time over the first axis 108 (e.g., fast axis) to ensure that small features (e.g., small feature 150 in FIG. 1B) on the second axis 110 (e.g., slow axis) are adequately scanned over the entire workpiece. However, when the fast scan speed is slowed to approach the slow scan speed, it is difficult to ensure dose uniformity when very sharp features are present in the beam profile (e.g., small feature 150).
Therefore, aspects of the present disclosure relates to techniques for improving beam uniformity using a scanned ion beam.